Free Pregnancy Tool
How Many Weeks Pregnant
Find out how far along you are today, in weeks and days, from your last period or your due date.
General information only, not medical advice. Ask your doctor or midwife.
How this works
Formula: Weeks pregnant = (today − first day of last period) ÷ 7, or 40 weeks − (due date − today).
- Pregnancy is counted from the first day of your last period, so the calculator counts the days from then to today.
- If you enter a due date instead, it counts back 280 days to find the matching start date.
- It splits the days into whole weeks and leftover days, the way your care team writes it, for example 12 weeks, 3 days.
- Trimesters: the first runs to the end of week 13, the second from week 14 to the end of week 27, the third from week 28.
Everything is worked out in your browser. Belly Weekly does not send or store your answers.
Questions
Why does pregnancy start before I was pregnant?
Counting from the last period is the standard because that date is easier to know than the day of conception.
What does 12+3 mean?
12 weeks and 3 days pregnant.
When is a baby full term?
Full term is 39 weeks 0 days through 40 weeks 6 days.